The study concerns the survival, regeneration and axonal growth of isolated neuronal groups during development using the tissue culture technique. The organ of Corti of the mouse at different developmental ages will be the tissue of choice. Morphological observations will be made using light microscopy for the study of live tissue; light microscopy, SEM and TEM techniques for the study of fixed material. The proposed project includes: 1. Study of the growth of the peripheral fibers of the spiral neurons in response to the absence or disruption of neurosensory contacts; 2. Study of the development of the afferent innervation formed by the peripheral fibers of spiral neurons in the organ of Corti of the fetal mouse; 3. Study of the survival and differentiation of the spiral ganglion cells in the organ of Corti of the postnatal mouse; 4. Ultrastructural study of neurosensory synapses in the organotypic cultures of the organ of Corti of the newborn mouse. BIBLIOGRAPHIC REFERENCES: Sobkowicz, H.M., Bereman, B., and Rose, J.E. 1975. Organotypic development of the organ of Corti in culture. J. Neurocytol., 4: 543-572.